Nuclear magnetic resonance spectrometry of alkyl ligands immobilized on reversed-phase liquid chromatographic surfaces

Gilpin, R. K.; Gangoda, Mahinda

doi:10.1021/ac00272a060

Cited by 87 publications

(45 citation statements)

References 32 publications

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“…7b) follows the "bristle brush", "haystack", "ink bottle", and other models presented by Halasz and Sebestian [21], Hemetsberger et al [22], Lochmuller and Wilder [27] and others [23][24][25]. These experiments reiterate the solution NMR experiments done on alkyl-chain derivatized HPLC silica particles packed within an NMR tube [9,12,[15][16][17][18]26,28,29,31,32], albeit, with the NMR Wool Tube experiments, more solvent mixtures were examined.…”

Section: The Spectral Characteristics Of the Bonded Phase In The Pressupporting

confidence: 57%

“…The concepts of the hydrophobic bonded phase configurations have evolved from the early static models [13,21] to more recent dynamic models where bonded chains can undergo changes in orientation and mobility dependent on various parameters such as temperature, solvent type and composition [26] or aggregate under defined conditions [27,28]. The dynamic models were further bolstered by studies [29] that showed that alkyl chains (i) possess a flexibility related to the mobile phase used and carbon content of the bonded phase, and (ii) that they exist in various conformations with the range extrema going from rigid brushes to a convoluted form.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

NMR Wool Tube: a novel method for NMR solution analysis of derivatized glass surfaces

Cholewa

2004

Journal of Chromatography A

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Section: The Spectral Characteristics Of the Bonded Phase In The Pressupporting

confidence: 57%

Section: Introductionmentioning

confidence: 99%

NMR Wool Tube: a novel method for NMR solution analysis of derivatized glass surfaces

Cholewa

2004

Journal of Chromatography A

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“…In order to characterize the behavior in solvent containing, modified systems, Gilpin and Gangoda (148,(192)(193)(194)(195)(196)(197) have performed experiments on a variety of 13C labelled silanes. In their initial studies, the labelling allowed them to observe the resonances from the labelled species at the interface.…”

Section: Studiesmentioning

confidence: 99%

“…These results suggested to the authors that the silanes were more orientationally ordered in the presence of solvents than in their absence. It is believed that the mobility of the chain is related to the behavior as separation medium (194,198).…”

Section: Studiesmentioning

confidence: 99%

NMR Studies of Organic Thin films

Blum

1994

Annual Reports on NMR Spectroscopy

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“…[5][6][7] This has been ascribed to increased chain ordering in polymeric phases, which results from their alkyl chain organization as a result of higher chain densities. 4,6,[8][9][10][11][12] and simulation 13 studies have shown that chain ordering increases with increasing chain density.…”

Section: Introductionmentioning

confidence: 99%

An Attempt Directed toward Enhanced Shape Selectivity in Reversed-Phase Liquid Chromatography: Preparation of the Dodecylaminated β-Cyclodextrin-Bonded Phase

et al. 2002

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Soluteshape selectivity in reversed-phase liquid chromatography (RPLC) has been a topic of much study over the last decade.1,2 Several classes of closely related compounds, such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls, steroids, and carotenoids, can be separated in RPLC based on the molecular shape. 3 Although the contribution of the reversed-phase material to shape selectivity is not completely understood, there have been a few trends observed in RPLC separations. Shape selectivity varies with carbon loading of the stationary phase, the length of the alkyl-chains bonded to silica gel and the properties of the silica substrate. Also, it is well known that shape selectivity is enhanced by reducing the column temperature or by increasing the organic-modifier content in the mobile phase. Furthermore, shape selectivity differences are strongly influenced by the kind of surface-modification chemistry used. 4 It has been noted that polymeric octadecylsilane (ODS) silicas provide higher shape selectivity than monomeric counterparts in the separation of PAHs. [5][6][7] This has been ascribed to increased chain ordering in polymeric phases, which results from their alkyl chain organization as a result of higher chain densities. 4,6,[8][9][10][11][12] and simulation 13 studies have shown that chain ordering increases with increasing chain density.The purpose of this paper is to report on the synthesis of a new RPLC bonded phase that is designed so as to have regularly spaced, ordered chains on a local level. The possible structure of the prepared stationary phase is depicted in Fig. 1. A number of PAHs were separated with this stationary phase, and its selectivity was compared with those obtained with conventional stationary phases. The preliminary experiments revealed that the new stationary phase offers enhanced molecular shape-recognition performance.It may be noted that, by far, a large number of modified β-CD stationary phases have been synthesized, most of which were directed toward chiral separations, but not toward RPLC separations. An exception to this trend has been presented by i and Ishizuka. 14 They synthesized dodecylamino-β-CD by the reaction of heptakis(6-bromo-6-deoxy)-β-CD with dodecylamine in dimethylformamide. ODS silicas were coated with the produced material and used as a stationary phase for the separation of structural isomers. Experimental Synthesis of the stationary phaseThe preparation procedure of the stationary phase consisted of four separate stages (Fig. 2): (1) silylation of silica gel through reactions of 3-glycidoxypropyltrimethoxysilane with the surface silanol groups, 15 which provides a site for subsequent bonding with dodecylaminated β-CD; (2) sulfonation of the primary hydroxyl groups of β-CD with mesitylsulfonyl chloride, 16 (3) reaction of n-dodecylamine with mesitylenesulfonylated β-CD, yielding n-dodecylamino-derivatized β-CD (DA-β-CD) (the synthesis of heptakis(6-dodecylamino-6-deoxy)-β-CD has been already described by Takahashi et al. 17 ); and (4...

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Nuclear magnetic resonance spectrometry of alkyl ligands immobilized on reversed-phase liquid chromatographic surfaces

Cited by 87 publications

References 32 publications

NMR Wool Tube: a novel method for NMR solution analysis of derivatized glass surfaces

NMR Wool Tube: a novel method for NMR solution analysis of derivatized glass surfaces

NMR Studies of Organic Thin films

An Attempt Directed toward Enhanced Shape Selectivity in Reversed-Phase Liquid Chromatography: Preparation of the Dodecylaminated β-Cyclodextrin-Bonded Phase

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